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c: Improve build_component_ref diagnostics [PR91134] 

On the following testcase (the first dg-error line) we emit a weird
diagnostics and even fixit on pointerpointer->member
where pointerpointer is pointer to pointer to struct and we say
'pointerpointer' is a pointer; did you mean to use '->'?
The first part is indeed true, but suggesting -> when the code already
does use -> is confusing.
The following patch adjusts callers so that they tell it if it is from
. parsing or from -> parsing and in the latter case suggests to dereference
the left operand instead by adding (* before it and ) after it (before ->).
Or would a suggestion to add [0] before -> be better?

2022-05-25  Jakub Jelinek  <jakub@redhat.com>

	PR c/91134
gcc/c/
	* c-tree.h (build_component_ref): Add ARROW_LOC location_t argument.
	* c-typeck.cc (build_component_ref): Likewise.  If DATUM is
	INDIRECT_REF and ARROW_LOC isn't UNKNOWN_LOCATION, print a different
	diagnostic and fixit hint if DATUM has pointer type.
	* c-parser.cc (c_parser_postfix_expression,
	c_parser_omp_variable_list): Adjust build_component_ref callers.
	* gimple-parser.cc (c_parser_gimple_postfix_expression_after_primary):
	Likewise.
gcc/objc/
	* objc-act.cc (objc_build_component_ref): Adjust build_component_ref
	caller.
gcc/testsuite/
	* gcc.dg/pr91134.c: New test.
This commit is contained in:
Jakub Jelinek 2022-05-25 14:21:54 +02:00
parent 329417d775
commit 7a3ee77a2e
6 changed files with 73 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
gcc/c/c-parser.cc
View File

@ -9235,8 +9235,9 @@ c_parser_postfix_expression (c_parser *parser)
if (c_parser_next_token_is (parser, CPP_NAME))
{
c_token *comp_tok = c_parser_peek_token (parser);
offsetof_ref = build_component_ref
(loc, offsetof_ref, comp_tok->value, comp_tok->location);
offsetof_ref
= build_component_ref (loc, offsetof_ref, comp_tok->value,
comp_tok->location, UNKNOWN_LOCATION);
c_parser_consume_token (parser);
while (c_parser_next_token_is (parser, CPP_DOT)
|| c_parser_next_token_is (parser,
@ -9263,9 +9264,11 @@ c_parser_postfix_expression (c_parser *parser)
break;
}
c_token *comp_tok = c_parser_peek_token (parser);
offsetof_ref = build_component_ref
(loc, offsetof_ref, comp_tok->value,
comp_tok->location);
offsetof_ref
= build_component_ref (loc, offsetof_ref,
comp_tok->value,
comp_tok->location,
UNKNOWN_LOCATION);
c_parser_consume_token (parser);
}
else
@ -10612,7 +10615,7 @@ c_parser_postfix_expression_after_primary (c_parser *parser,
finish = c_parser_peek_token (parser)->get_finish ();
c_parser_consume_token (parser);
expr.value = build_component_ref (op_loc, expr.value, ident,
comp_loc);
comp_loc, UNKNOWN_LOCATION);
set_c_expr_source_range (&expr, start, finish);
expr.original_code = ERROR_MARK;
if (TREE_CODE (expr.value) != COMPONENT_REF)
@ -10652,7 +10655,8 @@ c_parser_postfix_expression_after_primary (c_parser *parser,
build_indirect_ref (op_loc,
expr.value,
RO_ARROW),
ident, comp_loc);
ident, comp_loc,
expr.get_location ());
set_c_expr_source_range (&expr, start, finish);
expr.original_code = ERROR_MARK;
if (TREE_CODE (expr.value) != COMPONENT_REF)
@ -13171,6 +13175,7 @@ c_parser_omp_variable_list (c_parser *parser,
&& c_parser_next_token_is (parser, CPP_DEREF)))
{
location_t op_loc = c_parser_peek_token (parser)->location;
location_t arrow_loc = UNKNOWN_LOCATION;
if (c_parser_next_token_is (parser, CPP_DEREF))
{
c_expr t_expr;
@ -13181,6 +13186,7 @@ c_parser_omp_variable_list (c_parser *parser,
t_expr = convert_lvalue_to_rvalue (op_loc, t_expr,
true, false);
t = build_indirect_ref (op_loc, t_expr.value, RO_ARROW);
arrow_loc = t_expr.get_location ();
}
c_parser_consume_token (parser);
if (!c_parser_next_token_is (parser, CPP_NAME))
@ -13194,7 +13200,8 @@ c_parser_omp_variable_list (c_parser *parser,
tree ident = comp_tok->value;
location_t comp_loc = comp_tok->location;
c_parser_consume_token (parser);
t = build_component_ref (op_loc, t, ident, comp_loc);
t = build_component_ref (op_loc, t, ident, comp_loc,
arrow_loc);
}
/* FALLTHROUGH */
case OMP_CLAUSE_AFFINITY:

3
gcc/c/c-tree.h
View File

@ -699,7 +699,8 @@ extern struct c_expr convert_lvalue_to_rvalue (location_t, struct c_expr,
extern tree decl_constant_value_1 (tree, bool);
extern void mark_exp_read (tree);
extern tree composite_type (tree, tree);
extern tree build_component_ref (location_t, tree, tree, location_t);
extern tree build_component_ref (location_t, tree, tree, location_t,
location_t);
extern tree build_array_ref (location_t, tree, tree);
extern tree build_external_ref (location_t, tree, bool, tree *);
extern void pop_maybe_used (bool);

27
gcc/c/c-typeck.cc
View File

@ -2457,11 +2457,12 @@ should_suggest_deref_p (tree datum_type)
/* Make an expression to refer to the COMPONENT field of structure or
union value DATUM. COMPONENT is an IDENTIFIER_NODE. LOC is the
location of the COMPONENT_REF. COMPONENT_LOC is the location
of COMPONENT. */
of COMPONENT. ARROW_LOC is the location of the first -> operand if
it is from -> operator. */
tree
build_component_ref (location_t loc, tree datum, tree component,
location_t component_loc)
location_t component_loc, location_t arrow_loc)
{
tree type = TREE_TYPE (datum);
enum tree_code code = TREE_CODE (type);
@ -2577,11 +2578,23 @@ build_component_ref (location_t loc, tree datum, tree component,
/* Special-case the error message for "ptr.field" for the case
where the user has confused "." vs "->". */
rich_location richloc (line_table, loc);
/* "loc" should be the "." token. */
richloc.add_fixit_replace ("->");
error_at (&richloc,
"%qE is a pointer; did you mean to use %<->%>?",
datum);
if (TREE_CODE (datum) == INDIRECT_REF && arrow_loc != UNKNOWN_LOCATION)
{
richloc.add_fixit_insert_before (arrow_loc, "(*");
richloc.add_fixit_insert_after (arrow_loc, ")");
error_at (&richloc,
"%qE is a pointer to pointer; did you mean to dereference "
"it before applying %<->%> to it?",
TREE_OPERAND (datum, 0));
}
else
{
/* "loc" should be the "." token. */
richloc.add_fixit_replace ("->");
error_at (&richloc,
"%qE is a pointer; did you mean to use %<->%>?",
datum);
}
return error_mark_node;
}
else if (code != ERROR_MARK)

5
gcc/c/gimple-parser.cc
View File

@ -1800,7 +1800,7 @@ c_parser_gimple_postfix_expression_after_primary (gimple_parser &parser,
finish = c_parser_peek_token (parser)->get_finish ();
c_parser_consume_token (parser);
expr.value = build_component_ref (op_loc, expr.value, ident,
comp_loc);
comp_loc, UNKNOWN_LOCATION);
set_c_expr_source_range (&expr, start, finish);
expr.original_code = ERROR_MARK;
if (TREE_CODE (expr.value) != COMPONENT_REF)
@ -1848,7 +1848,8 @@ c_parser_gimple_postfix_expression_after_primary (gimple_parser &parser,
expr.value = build_component_ref (op_loc,
build_simple_mem_ref_loc
(op_loc, expr.value),
ident, comp_loc);
ident, comp_loc,
expr.get_location ());
set_c_expr_source_range (&expr, start, finish);
expr.original_code = ERROR_MARK;
if (TREE_CODE (expr.value) != COMPONENT_REF)

2
gcc/objc/objc-act.cc
View File

@ -2812,7 +2812,7 @@ objc_build_component_ref (tree datum, tree component)
tf_warning_or_error);
#else
return build_component_ref (input_location, datum, component,
UNKNOWN_LOCATION);
UNKNOWN_LOCATION, UNKNOWN_LOCATION);
#endif
}

32
gcc/testsuite/gcc.dg/pr91134.c Normal file
View File

@ -0,0 +1,32 @@
/* PR c/91134 */
/* { dg-options "-fdiagnostics-show-caret" } */
struct X { int member; } x;
struct Y { struct X **x; } y;
int
foo (void)
{
struct X *pointer = &x;
struct Y *yp = &y;
struct X **pointerpointer = &pointer;
int i = *pointerpointer->member; /* { dg-error "'pointerpointer' is a pointer to pointer; did you mean to dereference it before applying '->' to it\\\?" } */
/* { dg-begin-multiline-output "" }
int i = *pointerpointer->member;
^~
(* )
{ dg-end-multiline-output "" } */
int j = pointer.member; /* { dg-error "'pointer' is a pointer; did you mean to use '->'\\\?" } */
/* { dg-begin-multiline-output "" }
int j = pointer.member;
^
->
{ dg-end-multiline-output "" } */
int k = yp->x->member; /* { dg-error "'yp->x' is a pointer to pointer; did you mean to dereference it before applying '->' to it\\\?" } */
/* { dg-begin-multiline-output "" }
int k = yp->x->member;
^~
(* )
{ dg-end-multiline-output "" } */
return i + j + k;
}